The embodiments described herein relate generally to a wind turbine rotor blade and, more particularly, to a sparcap for a wind turbine rotor blade.
Wind turbine blades typically include two blade shell portions of fiber reinforced polymer. The blade shell portions are molded and then coupled together along cooperating edges using a suitable adhesive material. At least some turbine blades include one or more bracings that are adhesively coupled to an inner surface of a first blade shell portion. A cooperating second blade shell portion is then arranged on top of the bracings and adhesively coupled to the first blade shell portion along its edges.
The blade shell portions are typically made using suitable evenly distributed fibers, fiber bundles, or mats of fibers layered in a mold part. However, the blade shell portions are relatively light and have only low rigidity. Therefore, a stiffness and a rigidity, as well as a buckling strength, of the blade shell portions may not withstand the loads and forces exerted on the rotor blade during operation. To increase the strength of the rotor blade, the blade shell portions are reinforced by sparcaps laminated to the inner surface of the blade shell portions.
Flapwise loads, which cause the rotor blade tip to deflect towards the wind turbine tower, are transferred along the rotor blade predominantly through the sparcaps. At least some conventional rotor blades include sparcaps fabricated from a suitable carbon material. The stiffness requirements of the conventional wind turbine rotor blade designs may be met by a completely carbon sparcap, but with an undesirable mass and/or cost penalty.
As a length of wind turbine rotor blades continues to increase, meeting stiffness requirements is a major concern in the structural design of the rotor blades. Conventional rotor blades including sparcaps made only of a carbon material meet the strength and stiffness requirements of the rotor blade but the sparcap does not have a sufficient buckling stiffness to meet the buckling factor of 1.25 required by current design certification standards. As a result, in at least some conventional rotor blades a thickness of the carbon material sparcap is increased to increase the buckling factor. Such increased thickness, however, results in a mass penalty and a fabrication cost penalty, as well as an undesirable increase in bending stiffness of the rotor blade.